Ansible 2.20 has deprecated the use of Ansible facts as variables. For
example, `ansible_distribution` is now deprecated in favor of
`ansible_facts["distribution"]`. This is due to making the default
setting `INJECT_FACTS_AS_VARS=false`. For now, this will create WARNING
messages, but in Ansible 2.24 it will be an error.
In order to ensure that commits and PRs conform to this, use
ANSIBLE_INJECT_FACT_VARS=false by default in our CI testing.
Update README-ostree.md if needed.
See https://docs.ansible.com/projects/ansible/latest/porting_guides/porting_guide_core_2.20.html#inject-facts-as-vars
Signed-off-by: Rich Megginson <rmeggins@redhat.com>